Packaged and processed foods, such as cakes, cookies, candies, chocolate, yogurt, and marshmallows, often contain unfamiliar animal ingredients, so may be a special concern for vegetarians due to the likelihood of such additions.[3][5] Often, prior to purchase or consumption, vegetarians will scrutinize products for animal-derived ingredients.[5] Vegetarians' feelings vary with regard to these ingredients. For example, while some vegetarians may be unaware of animal-derived rennet's role in the production of cheese, and may therefore unknowingly consume the product,[3][6][7] other vegetarians may not take issue with its consumption.[3][4]

Semi-vegetarian diets consist largely of vegetarian foods but may include fish or poultry, or sometimes other meats, on an infrequent basis. Those with diets containing fish or poultry may define meat only as mammalian flesh and may identify with vegetarianism.[8][9] A pescetarian diet has been described as "fish but no other meat".[10] The common use association between such diets and vegetarianism has led vegetarian groups such as the Vegetarian Society to state that diets containing these ingredients are not vegetarian, because fish and birds are also animals.[11]

The term 'vegetarian' has been in use since 1839 to refer to what was previously described as a "vegetable diet". The word is commonly believed to be a compound of vegetable and the suffix -arian (as in agrarian). (John Davis shows that it was probably not derived from the Latin word vegetus.[12]) The term was popularized with the foundation of the Vegetarian Society in Manchester, UK in 1847.[13][14] The earliest occurrences of the term seem to be related to Alcott House, a school on the north side of Ham Common, London, opened in July 1838 by James Pierrepont Greaves. From 1841, it was known as A Concordium, or Industry Harmony College, from which time the institution began to publish its own pamphlet, "The Healthian", which provides some of the earliest appearances of the term "vegetarian".[15][16]

The earliest record of vegetarianism comes from Indus Valley Civilization[citation needed] as early as the 7th century BCE,[17] inculcating tolerance towards all living beings.[18][19] Vegetarianism was also practiced in ancient Greece and the earliest reliable evidence for vegetarian theory and practice in Greece dates from the 6th century BC. The Orphics, a religious movement spreading in Greece at that time, and Pythagoras, a philosopher and religious leader in the area of Southern Italy colonized by Greek settlers, abstained from the flesh of animals.[20]

Vegetarianism was also practiced about six centuries later in another instance (between 30 BCE–50 CE) in northern Thracian region, the Moesi tribe who inhabited present day Serbia and Bulgaria, feeding themselves on honey, milk and cheese.[21]

In the Indian culture, the diet was closely connected with the attitude of nonviolence towards animals (called ahimsa in India) and was promoted by religious groups and philosophers.[22] The ancient Indian work of Tirukkural explicitly and unambiguously emphasizes vegetarianism and non-killing.[23] Chapter 26 of the Tirukkural, through couplets 251 to 260, deals exclusively on vegetarianism or veganism.[23] Among the Hellenes, Egyptians and others, it had medical or ritual purification purposes.

"Twenty-six years after my coronation various animals were declared to be protected – parrots, mainas, aruna, ruddy geese, wild ducks, nandimukhas, gelatas, bats, queen ants, terrapins, boneless fish, vedareyaka, gangapuputaka, sankiya fish, tortoises, porcupines, squirrels, deer, bulls, okapinda, wild asses, wild pigeons, domestic pigeons and all four-footed creatures that are neither useful nor edible. Those nanny goats, ewes and sows which are with young or giving milk to their young are protected, and so are young ones less than six months old. Cocks are not to be caponized, husks hiding living beings are not to be burnt and forests are not to be burnt either without reason or to kill creatures. One animal is not to be fed to another." —Edicts of Ashoka, Fifth Pillar

Following the Christianization of the Roman Empire in late antiquity, vegetarianism practically disappeared from Europe, as it did on other continents, except India.[25] Several orders of monks in medieval Europe restricted or banned the consumption of meat for ascetic reasons, but none of them eschewed fish.[26] (The medieval definition of "fish" included such animals as seals, porpoises, dolphins, barnacle geese, puffins, and beavers.)[27] It re-emerged during the Renaissance,[28] becoming more widespread in the 19th and 20th centuries. In 1847, the first Vegetarian Society was founded in the United Kingdom;[29] Germany, the Netherlands, and other countries followed. In 1886, the vegetarian colony Nueva Germania was founded in Paraguay, though its vegetarian aspect would prove short-lived.[30]:345–358 The International Vegetarian Union, an association of the national societies, was founded in 1908. In the Western world, the popularity of vegetarianism grew during the twentieth century as a result of nutritional, ethical, and more recently, environmental and economic concerns.

There are a number of vegetarian diets that exclude or include various foods:

Buddhist vegetarianism. Different Buddhist traditions have differing teachings on diet, which may also vary for ordained monks and nuns compared to others. Many interpret the precept 'not to kill' to require abstinence from meat, but not all. In Taiwan, su vegetarianism excludes not only all animal products but also vegetables in the allium family (which have the characteristic aroma of onion and garlic): onion, garlic, scallions, leeks, chives, or shallots.

Fruitarianism permits only fruit, nuts, seeds, and other plant matter that can be gathered without harming the plant.[31]

Jain vegetarianism includes dairy but excludes eggs and honey, as well as root vegetables.

Veganism excludes all animal flesh and by-products, such as milk, honey (not always), and eggs, as well as items refined or manufactured through any such product, such as bone-char refined white sugar or animal-tested baking soda.

Raw veganism includes only fresh and uncooked fruit, nuts, seeds, and vegetables. Vegetables can only be cooked up to a certain temperature, for instance using a dehydrator.[32]

Within the "ovo-" groups, there are many who refuse to consume fertilized eggs (with balut being an extreme example); however, such distinction is typically not specifically addressed.

Some vegetarians also avoid products that may use animal ingredients not included in their labels or which use animal products in their manufacturing; for example, sugars that are whitened with bone char, cheeses that use animal rennet (enzymes from animal stomach lining), gelatin (derived from the collagen inside animals' skin, bones and connective tissue), some cane sugar (but not beet sugar) and apple juice/alcohol clarified with gelatin or crushed shellfish and sturgeon, while other vegetarians are unaware of or do not mind such ingredients.[3][4][5][6]

Individuals sometimes label themselves "vegetarian" while practicing a semi-vegetarian diet,[9][33][34] as some dictionary definitions describe vegetarianism as sometimes including the consumption of fish, or only include mammalian flesh as part of their definition of meat,[8][35] while other definitions exclude fish and all animal flesh.[11] In other cases, individuals may describe themselves as "flexitarian".[33][36] These diets may be followed by those who reduce animal flesh consumed as a way of transitioning to a complete vegetarian diet or for health, ethical, environmental, or other reasons. Semi-vegetarian diets include:

Macrobiotic diet consisting mostly of whole grains and beans, but may sometimes include fish.

Pescetarianism, which includes fish and possibly other forms of seafood;

"Pollo-pescetarian", which includes poultry and fish, or "white meat" only;

Pollotarianism, which includes chicken and possibly other poultry;

Semi-vegetarianism is contested by vegetarian groups, such as the Vegetarian Society, which states that vegetarianism excludes all animal flesh.[11]

On average, vegetarians consume a lower proportion of calories from fat (particularly saturated fatty acids), fewer overall calories, more fiber, potassium, and vitamin C, than do non-vegetarians. Vegetarians generally have a lower body mass index. These characteristics and other lifestyle factors associated with a vegetarian diet may contribute to the positive health outcomes that have been identified among vegetarians.

Studies on the health effects of vegetarian diets observe heterogeneous effects on mortality. One review found a decreased overall risk of all cause mortality, cancer (except breast) and cardiovascular disease,[38][38] however another meta analysis found lower risk for ischemic heart disease and cancer, but no effect on overall mortality or cerebrovascular disease. Possible limitations include varying definitions used of vegetarianism, and the observation of increased risk of lung cancer mortality in those on a vegetarian diet for less than five years.[39] An analysis pooling 2 large studies found vegetarians in the UK have similar all cause mortality as meat eaters.[40] An older meta analysis found similar results, only finding decreased mortality in vegetarians, pescatarians, and irregular meat eaters in ischemic heart disease, but not from any other cause.[41]

"Vegetarian diets can meet guidelines for the treatment of diabetes and some research suggests that diets that are more plant-based reduce risk of type-2 diabetes. Rates of self-reported Seventh-day Adventists (SDA) were less than half of those of the general population, and, among SDA, vegetarians had lower rates of diabetes than non-vegetarians. Among possible explanations for a protective effect of vegetarian diet are the Lower BMI of vegetarians and higher fiber intake, both of which improve insulin sensitivity."[47]

The relationship between vegetarian diet and bone health remains unclear. According to some studies, a vegetarian lifestyle can be associated with vitamin B 12 deficiency and low bone mineral density.[48] However, a study of vegetarian and non-vegetarian adults in Taiwan found no significant difference in bone mineral density between the two groups.[49] Other studies, exploring animal protein's negative effects on bone health, suggest that vegetarians may be less prone to osteoporosis than omnivores, as vegetarian subjects had greater bone mineral density[50] and more bone formation.[51]

A British study of almost 10,000 men found that those who gave up meat were almost twice as likely to suffer from depression as people on a conventional balanced diet. The study found that the 350 committed vegetarians studied had a higher average depression score compared to others.[54]

Protein intake in vegetarian diets is lower than in meat diets but can meet the daily requirements for most people.[58] Studies at Harvard University as well as other studies conducted in the United States, United Kingdom, Canada, Australia, New Zealand and various European countries, confirmed vegetarian diets provide sufficient protein intake as long as a variety of plant sources are available and consumed.[59] Pumpkin seeds, peanut butter, hemp seed, almonds, pistachio nuts, flaxseed, tofu, oats, soybeans, walnuts, are great sources of protein for vegetarians. Proteins are composed of amino acids, and a common concern with protein acquired from vegetable sources is an adequate intake of the essential amino acids, which cannot be synthesised by the human body. While dairy and egg products provide complete sources for ovo-lacto vegetarian, several vegetable sources have significant amounts of all eight types of essential amino acids, including lupin beans, soy,[60]hempseed, chia seed,[61]amaranth,[62]buckwheat,[63]pumpkin seeds[64]spirulina,[65]pistachios,[66] and quinoa.[67] However, the essential amino acids can also be obtained by eating a variety of complementary plant sources that, in combination, provide all eight essential amino acids (e.g. brown rice and beans, or hummus and whole wheat pita, though protein combining in the same meal is not necessary[citation needed]). A 1994 study found a varied intake of such sources can be adequate.[68]

The recommended dietary allowance of B12 in the United States is, per day, 0.4 mcg (0–6 months), rising to 1.8 mcg (9–13 years), 2.4 mcg (14+ years), and 2.8 mcg (lactating female).[75] While the body's daily requirement for vitamin B12 is very small, deficiency of the vitamin is very serious leading to anemia and irreversible nerve damage.[82]

Calcium intake in vegetarians and vegans can be similar to non-vegetarians, as long as the diet is properly planned.[87] Lacto-ovo vegetarians that include dairy products can still obtain calcium from dairy sources like milk, yogurt, and cheese.[88]

Non-dairy milks that are fortified with calcium, such as soymilk and almond milk can also contribute a significant amount of calcium in the diet.[89] The calcium found in broccoli, bok choy, and kale have also been found to have calcium that is well absorbed in the body.[87][88][90] Though the calcium content per serving is lower in these vegetables than a glass of milk, the absorption of the calcium into the body is higher.[88][90] Other foods that contain calcium include calcium-set tofu, blackstrap molasses, turnip greens, mustard greens, soybeans, tempeh, almonds, okra, dried figs, and tahini.[87][89] Though calcium can be found in Spinach, swiss chard, beans and beet greens, they are generally not considered to be a good source since the calcium binds to oxalic acid and is poorly absorbed into the body.[88] Phytic acid found in nuts, seeds, and beans may also impact calcium absorption rates.[88] See the National Institutes of Health Office of Dietary Supplements for calcium needs for various ages,[88] the Vegetarian Resource Group[89] and the Vegetarian Nutrition Calcium Fact Sheet from the Academy of Nutrition and Dietetics[87] for more specifics on how to obtain adequate calcium intake on a vegetarian or vegan diet.

Vitamin D needs can be met via the human body's own generation upon sufficient and sensible exposure to ultraviolet (UV) light in sunlight.[91][92] Products including milk, soy milk and cereal grains may be fortified to provide a source of Vitamin D.[93] For those who do not get adequate sun exposure or food sources, Vitamin D supplementation may be necessary.

Vitamin D2, or ergocalciferol is found in fungus (except alfalfa which is a plantae) and created from viosterol, which in turn is created when ultraviolet light activates ergosterol (which is found in fungi and named as a sterol from ergot). Any UV-irradiated fungus including yeast form vitamin D2.[96] Human bioavailability of vitamin D2 from vitamin D2-enhanced button mushrooms via UV-B irradiation is effective in improving vitamin D status and not different from a vitamin D2 supplement according to study.[97] For example, Vitamin D2 from UV-irradiated yeast baked into bread is bioavailable.[98] By visual assessment or using a chromometer, no significant discoloration of irradiated mushrooms, as measured by the degree of "whiteness", was observed[99] making it hard to discover if they have been treated without labeling. Claims have been made that a normal serving (approx. 3 oz or 1/2 cup, or 60 grams) of mushrooms treated with ultraviolet light increase their vitamin D content to levels up to 80 micrograms,[100] or 2700 IU if exposed to just 5 minutes of UV light after being harvested.[101]

A 1999 metastudy combined data from five studies from western countries.[102] The metastudy reported mortality ratios, where lower numbers indicated fewer deaths, for fish eaters to be 0.82, vegetarians to be 0.84, occasional meat eaters (eat meat less than once per week) to be 0.84. Regular meat eaters had the base mortality rate of 1.0, while the number for vegans was very uncertain (anywhere between 0.7 and 1.44) due to too few data points. The study reported the numbers of deaths in each category, and expected error ranges for each ratio, and adjustments made to the data. However, the "lower mortality was due largely to the relatively low prevalence of smoking in these [vegetarian] cohorts". Out of the major causes of death studied, only one difference in mortality rate was attributed to the difference in diet, as the conclusion states: "...vegetarians had a 24% lower mortality from ischaemic heart disease than non-vegetarians, but no associations of a vegetarian diet with other major causes of death were established".[102]

In Mortality in British vegetarians,[103] a similar conclusion is drawn:

British vegetarians have low mortality compared with the general population. Their death rates are similar to those of comparable non-vegetarians, suggesting that much of this benefit may be attributed to non-dietary lifestyle factors such as a low prevalence of smoking and a generally high socio-economic status, or to aspects of the diet other than the avoidance of meat and fish."[104]

The Adventist Health Studies is ongoing research that documents the life expectancy in Seventh-day Adventists. This is the only study among others with similar methodology which had favourable indication for vegetarianism. The researchers found that a combination of different lifestyle choices could influence life expectancy by as much as 10 years. Among the lifestyle choices investigated, a vegetarian diet was estimated to confer an extra 1–1/2 to 2 years of life. The researchers concluded that "the life expectancies of California Adventist men and women are higher than those of any other well-described natural population" at 78.5 years for men and 82.3 years for women. The life expectancy of California Adventists surviving to age 30 was 83.3 years for men and 85.7 years for women.[105]

The Adventist health study is again incorporated into a metastudy titled "Does low meat consumption increase life expectancy in humans?" published in American Journal of Clinical Nutrition, which concluded that low meat eating (less than once per week) and other lifestyle choices significantly increase life expectancy, relative to a group with high meat intake. The study concluded that "The findings from one cohort of healthy adults raises the possibility that long-term (≥ 2 decades) adherence to a vegetarian diet can further produce a significant 3.6-y increase in life expectancy." However, the study also concluded that "Some of the variation in the survival advantage in vegetarians may have been due to marked differences between studies in adjustment for confounders, the definition of vegetarian, measurement error, age distribution, the healthy volunteer effect, and intake of specific plant foods by the vegetarians." It further states that "This raises the possibility that a low-meat, high plant-food dietary pattern may be the true causal protective factor rather than simply elimination of meat from the diet." In a recent review of studies relating low-meat diet patterns to all-cause mortality, Singh noted that "5 out of 5 studies indicated that adults who followed a low meat, high plant-food diet pattern experienced significant or marginally significant decreases in mortality risk relative to other patterns of intake."[106]

Statistical studies, such as comparing life expectancy with regional areas and local diets in Europe also have found life expectancy considerably greater in southern France, where a low meat, high plant Mediterranean diet is common, than northern France, where a diet with high meat content is more common.[107]

A study by the Institute of Preventive and Clinical Medicine, and Institute of Physiological Chemistry looked at a group of 19 vegetarians (lacto-ovo) and used as a comparison a group of 19 omnivorous subjects recruited from the same region. The study found that this group of vegetarians (lacto-ovo) have a significantly higher amount of plasma carboxymethyllysine and advanced glycation endproducts (AGEs) compared to this group of non-vegetarians.[108] Carboxymethyllysine is a glycation product which represents "a general marker of oxidative stress and long-term damage of proteins in aging, atherosclerosis and diabetes" and "[a]dvanced glycation end products (AGEs) may play an important adverse role in process of atherosclerosis, diabetes, aging and chronic renal failure".[108]

In Western medicine, patients are sometimes advised[by whom?] to adhere to a vegetarian diet.[109] According to studies by the Permanente Journal and the National Institute for Health (NIH), vegetarian diets are affordable and can help reduce health risks like high blood pressure, cardiovascular disease, and cholesterol levels. A plant based diet has the potential to lower the risk of heart disease as well as reducing the amount of medications prescribed in instances of chronic illness. A change to a plant based diet, or vegetarianism, has had dramatic positive effects on the health of patients with chronic illnesses, significantly more than exercise alone [110] Vegetarian diets have been used as a treatment for rheumatoid arthritis, but the evidence is inconclusive whether this is effective.[111] Certain alternative medicines, such as Ayurveda and Siddha, prescribe a vegetarian diet as a normal procedure. Maya Tiwari notes that Ayurveda recommends small portions of meat for some people, though "the rules of hunting and killing the animal, practiced by the native peoples, were very specific and detailed". Now that such methods of hunting and killing are not observed, she does not recommend the use of "any animal meat as food, not even for the Vata types".[112]

The American Dietetic Association has presented evidence that vegetarian diets may be more common among adolescents with eating disorders. At the same time the association cautions however, that the adoption of a vegetarian diet may not necessarily lead to eating disorders, rather that "vegetarian diets may be selected to camouflage an existing eating disorder".[117] Other studies and statements by dietitians and counselors support this conclusion.[nb 1][119]

Various ethical reasons have been suggested for choosing vegetarianism, usually predicated on the interests of non-human animals. In many societies, controversy and debate have arisen over the ethics of eating animals. Some people, while not vegetarians, refuse to eat the flesh of certain animals due to cultural taboo, such as cats, dogs, horses or rabbits. Others support meat eating for scientific, nutritional and cultural reasons, including religious ones. Some meat eaters abstain from the meat of animals reared in particular ways, such as factory farms, or avoid certain meats, such as veal or foie gras. Some people follow vegetarian or vegan diets not because of moral concerns involving the raising or consumption of animals in general, but because of concerns about the specific treatment and practises involved in the raising and slaughter of animals, i.e. factory farming and the industrialisation of animal slaughter. Others still avoid meat because meat production is claimed to place a greater burden on the environment than production of an equivalent amount of plant protein.

Ethical objections based on consideration for animals are generally divided into opposition to the act of killing in general, and opposition to certain agricultural practices surrounding the production of meat.

Princeton University professor and founder of the animal rights movement, Peter Singer, believes that if alternative means of survival exist, one ought to choose the option that does not cause unnecessary harm to animals. Most ethical vegetarians argue that the same reasons exist against killing animals to eat as against killing humans to eat. Singer, in his book Animal Liberation listed possible qualities of sentience in non-human creatures that gave such creatures the scope to be considered under utilitarian ethics, and this has been widely referenced by animal rights campaigners and vegetarians. Ethical vegetarians also believe that killing an animal, like killing a human, can only be justified in extreme circumstances and that consuming a living creature for its enjoyable taste, convenience, or nutrition value is not a sufficient cause. Another common view is that humans are morally conscious of their behaviour in a way other animals are not, and therefore subject to higher standards.[120]

Opponents of ethical vegetarianism argue that animals are not moral equals to humans and so consider the comparison of eating livestock with killing people to be fallacious. This view does not excuse cruelty, but maintains that animals do not possess the rights a human has.[121]

To produce milk from dairy cattle, calves are separated from their mothers soon after birth and slaughtered or fed milk replacer in order to retain the cows milk for human consumption.[123] Vegans state that this breaks the natural mother and calf bond.[123] Unwanted male calves are either slaughtered at birth or sent for veal production.[123] To prolong lactation, dairy cows are almost permanently kept pregnant through artificial insemination.[123] After about five years, once the cows milk production has dropped, they are considered "spent" and sent to slaughter for beef and their hides. A dairy cow's natural life expectancy is about twenty years.[122]

Ethical vegetarianism has become popular in developed countries particularly because of the spread of factory farming, faster communications, and environmental consciousness. Some believe that the current mass demand for meat cannot be satisfied without a mass-production system that disregards the welfare of animals, while others believe that practices like well-managed free-ranging and consumption of game, particularly from species whose natural predators have been significantly eliminated, could substantially alleviate the demand for mass-produced meat.[citation needed]

Ancient Greek philosophy has a long tradition of vegetarianism. Pythagoras was reportedly vegetarian (and studied at Mt. Carmel, where some historians say there was a vegetarian community), as his followers were expected to be.

Roman writer Ovid concluded his magnum opus Metamorphoses, in part, with the impassioned argument (uttered by the character of Pythagoras) that in order for humanity to change, or metamorphose, into a better, more harmonious species, it must strive towards more humane tendencies. He cited vegetarianism as the crucial decision in this metamorphosis, explaining his belief that human life and animal life are so entwined that to kill an animal is virtually the same as killing a fellow human.

Everything changes; nothing dies; the soul roams to and fro, now here, now there, and takes what frame it will, passing from beast to man, from our own form to beast and never dies...Therefore lest appetite and greed destroy the bonds of love and duty, heed my message! Abstain! Never by slaughter dispossess souls that are kin and nourish blood with blood![125]

Indian cuisine offers a wide range of vegetarian delicacies because the two main sects of Hinduism, practised by the majority of India's population, encourage a vegetarian diet. Shown here is a vegetarian thali.

While there are no dietary restrictions in the Bahá'í Faith, `Abdu'l-Bahá, the son of the religion's founder, noted that a vegetarian diet consisting of fruits and grains was desirable, except for people with a weak constitution or those that are sick.[132] He stated that there are no requirements that Bahá'ís become vegetarian, but that a future society should gradually become vegetarian.[132][133][134] `Abdu'l-Bahá also stated that killing animals was contrary to compassion.[132] While Shoghi Effendi, the head of the Bahá'í Faith in the first half of the 20th century, stated that a purely vegetarian diet would be preferable since it avoided killing animals,[135] both he and the Universal House of Justice, the governing body of the Bahá'ís have stated that these teachings do not constitute a Bahá'í practice and that Bahá'ís can choose to eat whatever they wish but should be respectful of others' beliefs.[132]

Theravadins in general eat meat.[136] If Buddhist monks "see, hear or know" a living animal was killed specifically for them to eat, they must refuse it or else incur an offense.[137] However, this does not include eating meat which was given as alms or commercially purchased. In the Theravada canon, Buddha did not make any comment discouraging them from eating meat (except specific types, such as human, elephant meat, horse, dog, snake, lion, tiger, leopard, bear, and hyena flesh[138]) but he specifically refused to institute vegetarianism in his monastic code when a suggestion had been made.[139][140]

In several Sanskrit texts of Mahayana Buddhism, Buddha instructs his followers to avoid meat.[141][142][143][144] However, each branch of Mahayana Buddhism selects which sutra to follow, and some branches, including the majority of Tibetan and Japanese Buddhists, do eat meat, while many Chinese Buddhist branches do not.

Christians have always been free to make their own decisions about what to eat; however, there are groups within Christianity that practice specific dietary restrictions for various reasons.[145] The early sect known as the Ebionites are considered to have practiced vegetarianism. Surviving fragments from their Gospel indicate their belief that – as Christ is the Passover sacrifice and eating the Passover lamb is no longer required – a vegetarian diet may (or should) be observed. However, orthodox Christianity does not accept their teaching as authentic. Indeed, their specific injunction to strict vegetarianism was cited as one of the Ebionites' "errors".[146][147]

Seventh-day Adventists are encouraged to engage in healthy eating practices, and ova-lacto-vegetarian diets are recommended by the General Conference of Seventh-day Adventists Nutrition Council (GCNC). They have also sponsored and participated in many scientific studies exploring the impact of dietary decisions upon health outcomes.[151] The GCNC has in addition adapted the USDA's food pyramid for a vegetarian dietary approach.[151][152] However, the only kinds of meat specifically frowned upon by the SDA health message are unclean meats, or those forbidden in scripture.[153]

Additionally, some monastic orders follow a vegetarian diet, and members of the Orthodox Church follow a vegan diet during fasts.[154] There is also a strong association between the Quakers and vegetarianism dating back at least to the 18th century. The association grew in prominence during the 19th century, coupled with growing Quaker concerns in connection with alcohol consumption, anti-vivisection and social purity. The association between the Quaker tradition and vegetarianism, however, becomes most significant with the founding of the Friends' Vegetarian Society in 1902 "to spread a kindlier way of living amongst the Society of Friends."[155]

According to Canon Law, Roman Catholics are required to abstain from meat (defined as all animal flesh excluding water animals) on Ash Wednesday and all Fridays of Lent including Good Friday. Canon Law also obliges Catholics to abstain from meat on the Fridays of the year outside of Lent (excluding certain holy days) unless, with the permission of the local conference of bishops, another penitential act is substituted. The restrictions on eating meat on these days is solely as an act of penance and not because of a religious objection to eating meat.[156]

Since the formation of the Seventh-day Adventist Church in the 1860s when the church began, wholeness and health have been an emphasis of the Adventist church, and has been known as the "health message" belief of the church.[157] Adventists are well known for presenting a health message that recommends vegetarianism and expects adherence to the kosher laws in Leviticus 11. Obedience to these laws means abstinence from pork, shellfish, and other animals proscribed as "unclean". The church discourages its members from consuming alcoholic beverages, tobacco or illegal drugs (compare Christianity and alcohol). In addition, some Adventists avoid coffee, tea, cola, and other beverages containing caffeine. Adventist who follow the vegetarian lifestyle tend to live up to 10 years longer than people who do eat meat.[158] Adventists believe in taking care of one's body and eating as God intended from the Garden of Eden, all natural fruits, grains, nuts and vegetables.

Research funded by the U.S. National Institutes of Health has shown that the average Adventist in California lives 4 to 10 years longer than the average Californian. The research, as cited by the cover story of the November 2005 issue of National Geographic, asserts that Adventists live longer because they do not smoke or drink alcohol, have a day of rest every week, and maintain a healthy, low-fat vegetarian diet that is rich in nuts and beans.[160][161] The cohesiveness of Adventists' social networks has also been put forward as an explanation for their extended lifespan.[162] Since Dan Buettner's 2005 National Geographic story about Adventist longevity, his book, The Blue Zones: Lessons for Living Longer From the People Who've Lived the Longest, named Loma Linda, California a "blue zone" because of the large concentration of Seventh-day Adventists. He cites the Adventist emphasis on health, diet, and Sabbath-keeping as primary factors for Adventist longevity.[163][164]

An estimated 35% of Adventists practice vegetarianism or veganism, according to a 2002 worldwide survey of local church leaders.[165][166]

Adventists' clean lifestyles were recognized by the U.S. military in 1954 when 2,200 Adventists volunteered for Operation Whitecoat to be human test subjects for a range of diseases the effects of which were still unknown:

The first task for the scientists was to find people willing to be infected by pathogens that could make them very sick. They found them in the followers of the Seventh-day Adventist faith. Although willing to serve their country when drafted, the Adventists refused to bear arms. As a result many of them became medics. Now the U.S. was offering recruits an opportunity to help in a different manner: to volunteer for biological tests as a way of satisfying their military obligations. When contacted in late 1954, the Adventist hierarchy readily agreed to this plan. For Camp Detrick scientists, church members were a model test population, since most of them were in excellent health and they neither drank, smoked, nor used caffeine. From the perspective of the volunteers, the tests gave them a way to fulfill their patriotic duty while remaining true to their beliefs.[167]

Hinduism is more of a practice that was classified as a religion. Though there is no strict rule on what to consume and what not to, paths of Hinduism hold vegetarianism as an ideal influenced by Jains. Some reasons are: the principle of nonviolence (ahimsa) applied to animals;[168] the intention to offer only "pure" (vegetarian) food to a deity and then to receive it back as prasad; and the conviction that a sentient diet is beneficial for a healthy body and mind and that non-vegetarian food is not recommended for a better mind and for spiritual development. Other reasons maybe lack of availability of meat and forced diet by rulers.

However, the food habits of Hindus vary according to their community, location, custom and varying traditions. Historically and currently, those Hindus who eat meat prescribe Jhatka meat,[169] while some Hindus believe that the cow is a holy animal whose slaughter for meat is forbidden. This belief varies according to region.[170]

Some followers of Islam, or Muslims, chose to be vegetarian for health, ethical, or personal reasons. However, the choice to become vegetarian for non-medical reasons can sometimes be controversial due to conflicting fatwas and differing interpretations of the Quran. Though some more traditional Muslims may keep quiet about their vegetarian diet, the number of vegetarian Muslims is increasing.[171][172]

In January 1996, The International Vegetarian Union announced the formation of the Muslim Vegetarian/Vegan Society.[174]

Many non-vegetarian Muslims will select vegetarian (or seafood) options when dining in non-halal restaurants. However, this is a matter of not having the right kind of meat rather than preferring not to eat meat on the whole.[172]

Followers of Jainism believe that all living organisms whether they are micro-organism are living and have a soul, and have one or more senses out of five senses and they go to great lengths to minimise any harm to any living organism. Most Jains are lacto-vegetarians but more devout Jains do not eat root vegetables because they believe that root vegetables contain a lot more micro-organisms as compared to other vegetables, and that, by eating them, violence of these micro-organisms is inevitable. So they focus on eating beans and fruits, whose cultivation do not involve killing of a lot of micro-organisms. No products obtained from dead animals are allowed, because when a living beings dies, a lot of micro-organisms (called as decomposers) will reproduce in the body which decomposes the body, and in eating the dead bodies, violence of decomposers is inevitable. Jain monks usually do a lot of fasting, and when they knew through spiritual powers that their life is very little, they start fasting until death.[175][176] Some particularly dedicated individuals are fruitarians.[177] Honey is forbidden, because honey is the regurgitation of nectar by bees [178] and may also contain eggs, excreta and dead bees. Some Jains do not consume plant parts that grow underground such as roots and bulbs, because tiny animals may be killed when the plants are pulled up.[179]

While it is neither required (required only on special holidays [Pessach, Sukot and Shavuot] according to some traditions, but not on Shabbat [Friday], when just bread and wine/grape juice is required) nor prohibited for Jews to eat meat, a number of medieval scholars of Jewish religion (e.g., Joseph Albo and Isaac Arama) regard vegetarianism as a moral ideal, not just because of a concern for the welfare of animals, but because the slaughter of animals might cause the individual who performs such acts to develop negative character traits. One modern-day scholar who is in favour of vegetarianism is the late Rabbi Abraham Isaac Kook, the Chief Rabbi of Mandate Palestine. In his writings, Rabbi Kook speaks of vegetarianism as an ideal, and points to the fact that Adam did not partake of the flesh of animals, as all humans and animals were originally commanded by God to only eat plants.[180] In context, Rabbi Kook makes those comments in his portrayal of the eschatological (messianic) era. However, he personally refrained from eating meat except on the Sabbath and Festivals, and one of his leading disciples, Rabbi David Cohen, known as the "Nazirite" of Jerusalem, was a devout vegetarian. Several other members of Rabbi Kook's circle were also vegetarians.

According to some Kabbalists, only a mystic, who is able to sense and elevate the reincarnated human souls and "divine sparks", is permitted to consume meat, though eating the flesh of an animal might still cause spiritual damage to the soul. A number of Orthodox Jewish vegetarian groups and activists promote such ideas and believe that the halakhic permission to eat meat is a temporary leniency for those who are not ready yet to accept the vegetarian diet.[181][182] Jewish law also commands people to ritually slaughter animals when killing them, and goes into precise detail on the rituals of both animal sacrifice and ordinary slaughter (shechita). According to medieval sage Rabbi Shlomo Ephraim Luntschitz, author of the Torah commentary Kli Yakar, the complexity of these laws was intended to discourage the consumption of meat and make it less painful for the animals.[183]

Within the Afro-Caribbean community, a minority are Rastafari and follow the dietary regulations with varying degrees of strictness. The most orthodox eat only "Ital" or natural foods, in which the matching of herbs or spices with vegetables is the result of long tradition originating from the African ancestry and cultural heritage of Rastafari.[184] "Ital", which is derived from the word vital, means essential to human existence. Ital cooking in its strictest form prohibits the use of salt, meat (especially pork), preservatives, colorings, flavorings and anything artificial.[185] Most Rastafari are vegetarian.[186]

The tenets of Sikhism do not advocate a particular stance on either vegetarianism or the consumption of meat,[187][188][189][190] but leave the decision of diet to the individual.[191] The tenth guru, Guru Gobind Singh, however, prohibited "Amritdhari" Sikhs, or those that follow the Sikh Rehat Maryada (the Official Sikh Code of Conduct)[192] from eating Kutha meat, or meat which has been obtained from animals which have been killed in a ritualistic way. This is understood to have been for the political reason of maintaining independence from the then-new Muslim hegemony, as Muslims largely adhere to the ritualistic halal diet.[187][191]

"Amritdharis" that belong to some Sikh sects (e.g. Akhand Kirtani Jatha, Damdami Taksal, Namdhari[193] and Rarionwalay,[194] etc.) are vehemently against the consumption of meat and eggs (though they do consume and encourage the consumption of milk, butter and cheese).[195] This vegetarian stance has been traced back to the times of the British Raj, with the advent of many new Vaishnava converts.[191] In response to the varying views on diet throughout the Sikh population, Sikh Gurus have sought to clarify the Sikh view on diet, stressing their preference only for simplicity of diet. Guru Nanak said that over-consumption of food (Lobh, Greed) involves a drain on the Earth's resources and thus on life.[196][197] Passages from the Guru Granth Sahib (the holy book of Sikhs, also known as the Adi Granth) say that it is "foolish" to argue for the superiority of animal life, because though all life is related, only human life carries more importance: "Only fools argue whether to eat meat or not. Who can define what is meat and what is not meat? Who knows where the sin lies, being a vegetarian or a non-vegetarian?"[191] The Sikh langar, or free temple meal, is largely lacto-vegetarian, though this is understood to be a result of efforts to present a meal that is respectful of the diets of any person who would wish to dine, rather than out of dogma.[190][191]

Environmental vegetarianism is based on the concern that the production of meat and animal products for mass consumption, especially through factory farming, is environmentallyunsustainable. According to a 2006 United Nations initiative, the livestock industry is one of the largest contributors to environmental degradation worldwide, and modern practices of raising animals for food contribute on a "massive scale" to air and water pollution, land degradation, climate change, and loss of biodiversity. The initiative concluded that "the livestock sector emerges as one of the top two or three most significant contributors to the most serious environmental problems, at every scale from local to global."[198]

In addition, animal agriculture is a large source of greenhouse gases. According to a 2006 report it is responsible for 18% of the world's greenhouse gas emissions as estimated in 100-year CO2 equivalents. Livestock sources (including enteric fermentation and manure) account for about 3.1 percent of US anthropogenic GHG emissions expressed as carbon dioxide equivalents.[199] This EPA estimate is based on methodologies agreed to by the Conference of Parties of the UNFCCC, with 100-year global warming potentials from the IPCC Second Assessment Report used in estimating GHG emissions as carbon dioxide equivalents.

Meat produced in a laboratory (called in vitro meat) may be more environmentally sustainable than regularly produced meat.[200] Reactions of vegetarians vary.[201] Rearing a relatively small number of grazing animals can be beneficial, as the Food Climate Research Network at Surrey University reports: "A little bit of livestock production is probably a good thing for the environment.[202]

In May 2009, Ghent, Belgium, was reported to be "the first [city] in the world to go vegetarian at least once a week" for environmental reasons, when local authorities decided to implement a "weekly meatless day". Civil servants would eat vegetarian meals one day per week, in recognition of the United Nations' report. Posters were put up by local authorities to encourage the population to take part on vegetarian days, and "veggie street maps" were printed to highlight vegetarian restaurants. In September 2009, schools in Ghent are due to have a weekly veggiedag ("vegetarian day") too.[203]

Some groups, such as PETA, promote vegetarianism as a way to offset poor treatment and working conditions of workers in the contemporary meat industry.[204] These groups cite studies showing the psychological damage caused by working in the meat industry, especially in factory and industrialised settings, and argue that the meat industry violates its labourers' human rights by assigning difficult and distressing tasks without adequate counselling, training and debriefing.[205][206][207] However, the working conditions of agricultural workers as a whole, particularly non-permanent workers, remain poor and well below conditions prevailing in other economic sectors.[208] Accidents, including pesticide poisoning, among farmers and plantation workers contribute to increased health risks, including increased mortality.[209] According to the International Labour Organization, agriculture is one of the three most dangerous jobs in the world.[210]

Similar to environmental vegetarianism is the concept of economic vegetarianism. An economic vegetarian is someone who practices vegetarianism from either the philosophical viewpoint concerning issues such as public health and curbing world starvation, the belief that the consumption of meat is economically unsound, part of a conscious simple living strategy or just out of necessity. According to the Worldwatch Institute, "Massive reductions in meat consumption in industrial nations will ease their health care burden while improving public health; declining livestock herds will take pressure off rangelands and grainlands, allowing the agricultural resource base to rejuvenate. As populations grow, lowering meat consumption worldwide will allow more efficient use of declining per capita land and water resources, while at the same time making grain more affordable to the world's chronically hungry."[211]

A 1992 market research study conducted by the Yankelovich research organisation concluded that "of the 12.4 million people [in the US] who call themselves vegetarian, 68% are female, while only 32% are male".[213]

At least one study indicates that vegetarian women are more likely to have female babies. A study of 6,000 pregnant women in 1998 "found that while the national average in Britain is 106 boys born to every 100 girls, for vegetarian mothers the ratio was just 85 boys to 100 girls".[214] Catherine Collins of the British Dietetic Association has dismissed this as a "statistical fluke" given that it is actually the male's genetic contribution which determines the sex of a baby.[214]

^Vesanto Melina, a British Columbian registered dietitian and author of Becoming Vegetarian, stresses there is no cause and effect relationship between vegetarianism and eating disorders, although people who have eating disorders may label themselves as vegetarians "so that they won't have to eat."[118] Indeed, research indicates that the large majority of vegetarian or vegan anorexics and bulimics chose their diets after the onset of their disease. The "restricted" eating patterns of vegetarianism and veganism can legitimize the removal of numerous high-fat, energy-dense foods such as meat, eggs, cheese. However, the eating pattern chosen by those with anorexia or bulimia nervosa is far more restrictive than a healthful vegetarian diet, eliminating nuts, seeds, avocados, and limiting overall caloric intake.

^"Frequently Asked Questions - Ingredients 1: Gelatine". International Vegetarian Union (IVU). Retrieved February 7, 2013. [S]ince the gelatin product is from hides or bones – not real flesh – and has undergone such significant changes, it is no longer considered 'fleishig' (meat) but 'pareve', and can be eaten with dairy products. ...Rennet is like gelatin in the sense that it's a common food additive but the foods containing it are often considered vegetarian.

^ abcde"Why Avoid Hidden Animal Ingredients?". The North American Vegetarian Society. Retrieved February 7, 2013. Surprisingly, some people who consider themselves vegetarian continue to consume products that contain remains of slaughtered animals such as gelatin (made from ground-up skin and bones, found in Jell-O, supplement capsules, and photographic film) and rennet (made from the lining of calves 'stomachs, used to coagulate hard cheese). Some of these people may be unaware that these hidden animal ingredients even exist. Others know about them but feel that they are just minor components of a product, and that their presence is therefore not important... Many people who do not eat meat for ethical reasons do use animal by-products that are obtained while the animals are still alive. Dairy is a good example, as many vegetarians who consume it rationalize their behavior by pointing out that cows are not killed in order to provide humans with this particular by-product.

^ abcForrest, Jamie (December 18, 2007). "Is Cheese Vegetarian?". Serious Eats. Retrieved July 9, 2010. Some vegetarians are OK eating cheeses made with animal rennet, but many will seek out ones made with vegetarian rennet, especially since the latter are quite prevalent nowadays.

^ abShorter Oxford English Dictionary (2002 and 2007) defines "vegetarian" (noun) as "A person who on principle abstains from animal food; esp. one who avoids meat but will eat dairy produce and eggs and sometimes also fish (cf. VEGAN noun)."

^OED vol. 19, second edition (1989), p. 476; Webster’s Third New International Dictionary p. 2537; The Oxford Dictionary of English Etymology, Oxford, 1966, p. 972; The Barnhart Dictionary of Etymology (1988), p. 1196; Colin Spencer, The Heretic's Feast. A History of Vegetarianism, London 1993, p. 252. The OED writes that the word came into general use after the formation of the Vegetarian Society at Ramsgate in 1847, though it offers two examples of usage from 1839 and 1842:

1839: "If I had had to be my own cook, I should inevitably become a vegetarian." (F. A. Kemble, Jrnl. Residence on Georgian Plantation (1863) 251)

1842: "To tell a healthy vegetarian that his diet is very uncongenial with the wants of his nature." (Healthian, Apr. 34) The 1839 occurrence remains under discussion; the Oxford English Dictionary's 1839 source is in fact an 1863 publication: Fanny Kemble, Journal of a Residence on a Georgian Plantation 1838–1839. The original manuscript has not been located.

^Cordain, Loren (2007). "Implications of Plio-pleistocene diets for modern humans". In Peter S. Ungar. Evolution of the human diet: the known, the unknown and the unknowable. pp. 264–5. "Since the evolutionary split between homininis and pongids approximately 7 million years ago, the available evidence shows that all species of hominins ate an omnivorous diet composed of minimally processed, wild-plant, and animal foods.

^"Buddhism and Vegetarianism, The Rationale for the Buddha's Views on the Consumption of Meat"Archived October 7, 2013, at the Wayback Machine. by Dr V. A. Gunasekara" 'The rule of vegetarianism was the fifth of a list of rules which Devadatta had proposed to the Buddha. Devadatta was the founder of the tapasa movement in Buddhism and his special rules involved ascetic and austere practices (forest-dwelling, wearing only rags, etc). The Buddha rejected all the proposed revisions of Devadatta, and it was in this context that he reiterated the tikoiparisuddha rule. (On this see the author's Western Buddhism and a Theravada heterodoxy, BSQ Tracts on Buddhism'

^I.J. Singh, Sikhs and Sikhism, Manohar, Delhi ISBN978-81-7304-058-0: "Throughout Sikh history, there have been movements or subsects of Sikhism which have espoused vegetarianism. I think there is no basis for such dogma or practice in Sikhism."

^Surindar Singh Kohli, Guru Granth Sahib, An Analytical Study, Singh Bros. Amritsar ISBN81-7205-060-7: "The ideas of devotion and service in Vaishnavism have been accepted by Adi Granth, but the insistence of Vaishnavas on vegetarian diet has been rejected."

^ abGopal Singh, History of the Sikh People, World Sikh Univ. Press, Delhi, ISBN978-81-7023-139-4: "Nowadays in the Community Kitchen attached to the Sikh temples, and called the Guru's Kitchen (or Guru-ka-langar), meat dishes are not served at all. Maybe it is on account of its being, perhaps, expensive or not easy to keep for long. Or perhaps the Vaishnava tradition is too strong to be shaken off."

^Gyani Sher Singh, Philosophy of Sikhism, Shiromani Gurdwara Parbandhak Committee, Amritsar: "As a true Vaisnavite, Kabir remained a strict vegetarian. Kabir, far from defying Brahmanical tradition as to the eating of meat, would not permit so much as the plucking of a flower (G.G.S. p. 479), whereas Nanak deemed all such scruples to be superstitions."